The project consists of a series of experiments designed to elucidate the rules of mitochondrial transmission genetics and the mechanisms which underlie those rules, using a combination of methods at the cellular and molecular levels. Yeast mitochondria serve as a model system for investigation of general questions concerning the interaction of multiple genomes within a cell, the behavior of organelles during asexual and sexual reproduction, and mechanisms of mutation and recombination. These studies will provide background information for future studies of the role of organelle genes in the development and evolution of organelles and organisms. Experiments probe the phenomena of vegetative segregation, uniparental inheritance, and biased transmission of organelle genes which are common to organelle genetics in most or all organisms and the origin of antibiotic-resistant mutant cells. Mechanisms of mitochondrial transmission genetics being explored include biased input of mitochondrial DNA into the zygote; random drift of gene frequencies due either to nonreciprocal recombination during random mating of DNA molecules, or to random replication of DNA molecules; packaging of mitochondrial DNA into mitochondria and nucleoids; the mixing of mitochondria and mitochondrial DNA molecules in zygotes; and the partitioning of molecules and mitochondria between mother and daughter cells at cell division.